Field of the Invention
The present invention relates in general to the field of turbochargers. More particularly, the present invention relates to lubrication of turbochargers.
Discussion of the Related Art
Internal combustion engines operate as an pumps. That is to say, they draw in air, combine it with fuel, and produce energy. This energy is realized as power when the air-fuel mixture is ignited. Afterward, the waste created by the combustion is expelled. All of this is typically accomplished in four strokes of the pistons.
As internal combustion engines are not perfectly efficient, there is always an amount of wasted energy that is expelled with the exhaust. Turbochargers harness some of the wasted energy by fitting more air into the engine's combustion chambers, which may then be combined with more fuel, and creates a greater amount of power. The turbocharger accomplishes this task by compressing the air molecules so that the air the engine draws in is more dense.
A turbocharger uses the hot, expanding exhaust gases leaving the engine after combustion. These gases are routed directly to the turbine wheel side of the turbocharger to make it rotate. That turbine wheel is connected by a shaft to a compressor wheel. As the turbine wheel spins faster and faster, it causes the compressor wheel, and shaft, to also spin quickly. The rotation of the compressor wheel pulls in ambient air and compresses it before pumping it into the engine's combustion chambers. The compressor wheel, shaft, and turbine rotate at speeds up to 150,000 rpm.
Fluid bearings are commonly required within the turbocharger to prevent failure of the shaft at such high rotation speeds. The fluid bearings support the shaft on a layer of oil that is pumped around the shaft, cooling it and preventing friction. The fluid bearings typically employ a bronze material, forming a journal surrounding the shaft. In recent times, ball bearings have become more prevalent. Use of ceramics and high temperature alloys has made ball bearings more prevalent in turbochargers. Ball bearings reduce the contact area the shaft and bearing have, reducing friction. As there still is an element of friction, oil is commonly used as a lubricant for any turbocharger, regardless of the bearing type.
Some systems utilize a sealed oil to lubricate the turbocharger. More commonly, the engine's oil ,system is plumbed into the turbocharger's bearings to provide lubrication. Oil is commonly used as oil technology provides a low-cost friction reducing material that can withstand the temperatures and pressures of exhaust gases produced by an internal combustion chamber and withstand rotational speeds up to 150,000 rpm.
The use of oil is not, however, without its drawbacks. The shaft still comes in contact with the bearings, even if they are ball bearings. Oil's lubrication properties break down after use and exposure to the harsh environments of an internal combustion engine. This requires repeated maintenance of draining and filtering the oil. Oil is also an expensive commodity that has risen in price over recent decades.
What is therefore needed is an improved lubrication device that can withstand the volatile environments a turbocharger produces, while offering proper cooling and lubrication to a turbocharger's bearings. An additional need is for a turbocharger bearing that further reduces the friction a shaft is subjected to. Lastly, the lubrication would preferably be renewable, low cost, and readily available to all turbo-charging enthusiasts.